Client data signals, such as Gigabit Ethernet (GigE), Fibre Channel (FC), Enterprise Systems Connection (ESCON), International Business Machines InterSystem Channel-2/3 (IBM ISC-2/3) client data signals, and the like, are typically transported over telecommunications transport networks, such as Synchronous Digital Hierarchy/Synchronous Optical Networks (SDH/SONETs), Optical Transport Networks (OTNs), and the like, in one of two ways: 1) data frames are recovered from an incoming client data stream by terminating and stripping inter-frame information and encapsulating the data frames within some other protocol for transport, such as Point-to-Point Protocol (PPP), High-Level Data Link Control Protocol (HDLC), Generic Framing Procedure-F Protocol (GFP-F), or the like; or 2) the raw client data stream including the inter-frame information is re-encoded into an encapsulating protocol for transport, such as Generic Framing Procedure-T Protocol (GFP-T) or the like. Once the client data signal has been transported across the network, it is recovered from the encapsulating protocol. In both cases, rate adaptation of the outgoing client data stream, which is typically clocked by a local oscillator, is performed using a process involving idle character insertion/deletion. The method of insertion/deletion of idle characters is specific to the type of client data stream involved.
The methods described above suffer from the following shortcomings. The first method is not fully transparent because the inter-frame information is terminated and stripped prior to encapsulation. This creates problems for some client data signals that make use of the inter-frame information for management or other purposes. The second method is transparent but suffers from error multiplication occurring within the encapsulating protocol. For example, a multiple bit error within a GFP-T superblock results in the loss of 64 code words. Additionally, both methods perform rate adaptation of the outgoing client data signal through the insertion/deletion of idle characters specific to each client data signal type. This requires application-specific functions that increase complexity. Some client data signals, such as IBM ISC-2/3 client data signals, are not publicly standardized and the insertion/deletion of idle characters may cause improper operation. For such client data signals, a method for the transparent mapping/demapping of client data signals that does not rely on the insertion/deletion of idle characters for the rate adaptation of the outgoing client data signal is desirable.